1. Field of the Invention
The present invention relates to a carriage conveying apparatus and, particularly to an elevated carriage conveying apparatus for moving push carriages conveyed by operators from one work station to another.
2. Description of the Related Art
Work boards or wire laying boards generally are used to produce wiring harnesses. The wire laying boards are disposed on carriages that circulate on a conveyance path of an endless conveyor. However, some wire laying boards are placed on push carriages, which are conveyed by hand and are circulated from one work station to another.
A carriage conveying apparatus that uses the aforementioned push carriages needs to be installed in a relatively concentrated layout and the individual carriages need to be circulated in a very limited space. However, an inexpensive conveying apparatus that can circulate push carriages in a small space has not yet been developed. Such a carriage conveying apparatus could be connected with a main conveyor for assembling a plurality of sub-modules into a wiring harness. However, the connected conveying apparatus would take up a large space, and would disadvantageously enlarge a work line.
In view of the above, an object of the invention is to provide an inexpensive carriage conveying apparatus that can efficiently circulate carriages even in a limited space, and that can particularly push carriages in a limited space.
The subject invention is directed a carriage conveying apparatus that comprises a forward path for moving carriages substantially linearly from one work station to another, and a return path for moving the carriages from a downstream end of the forward path to an upstream end thereof. Thus, the carriages can be transferred easily from one path to the other.
The return path for circulating the carriages is formed immediately below the forward path for conveying the carriages from one work station to another. Thus, a circulating path that is compact in plan view can be constructed. Even if this elevated carriage conveying apparatus is connected with a main conveyor in a branched manner to construct a production line, it can be installed in a maximally concentrated layout.
According to a preferred embodiment of the invention, the return path is inclined such that the carriages return from an upstream side of the return path to a downstream side thereof at least partly by the action of gravity.
Preferably, the carriages are conveyed from the upstream end of the forward path to the downstream end thereof by being pushed by the operators.
The conveyors may comprise elevating tables that can elevated and lowered between upper and lower transfer positions. The carriages can be transferred between the upper transfer position and the forward path. Similarly, the carriages can be transferred between the lower transfer positions and the return path. The conveyors may further comprise driving units for elevating and lowering the elevating tables between the upper and lower transfer positions.
The carriage conveying apparatus preferably comprises at least one position detecting means for detecting elevated and/or lowered positions of the elevating tables in the corresponding transfer positions. Additionally, the carriage conveying apparatus preferably comprises a control unit for controlling operations of the driving units in accordance with signals from the position detecting means. Most preferably, the control unit permits the elevating table at the upstream side of the return path to be lowered only when the elevating table at the downstream side of the return path is in the lower transfer position.
The elevated conveyors enable the carriages to be transferred from the downstream end of the return path to the elevating table even if the carriages are conveyed from the upstream side to the downstream side of the return path by the action of gravity.
Preferably, carriage detection sensors are provided in the upper and lower transfer positions of the respective elevated conveyors for detecting the presence of a carriage. The carriage detection sensors are connected with the control unit such that detection signals can be inputted to the control unit. In such a case, the control unit can execute a more precise control.
Each driving unit may comprise a parallel link or pantograph system for supporting the elevating table such that the elevating table can be elevated and lowered, and preferably a single air cylinder for driving the parallel link. With such a driving unit, each elevating table can be elevated and lowered between the upper and lower transfer positions by the single air cylinder.
The conveyors may comprise temporary holding means for temporarily or releasably holding or locking the carriage positioned thereon during the transfer from one path to the other.
These and other objects, features and advantages of the present invention will become apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings.